1. Field of the Invention
The invention relates to a control device for an automatic transmission, and more particularly, to a control device for an automatic transmission capable of performing a process from a shift transmission starting to a shift transmission completion in a short time.
2. Description of the Related Art
An automatic transmission is provided with a plurality of gear pairs (input shaft-side gear and output shaft-side gear) of a constant mesh type between a rotary shaft of an input-side and a rotary shaft of an output-side, a synchromesh mechanism for switching the gear pairs between a power transmission state and a power non-transmission state by using an actuator, and a switching apparatus for applying a load to the synchromesh mechanism by the actuator and to switch a coupling state of the gear pairs and the rotary shafts. In the related art, a control device for the automatic transmission operates the synchromesh mechanism by the switching apparatus and to shift the automatic transmission to a desired shift transmission ratio.
In the control device for the automatic transmission, an automatic clutch is applied for power transmission between an engine that is a motor and the automatic transmission. If a shift disengagement operation for switching the gear pairs of the transmission starts immediately at the time of releasing the automatic clutch upon shift transmission control, a torsional vibration occurs in the rotary shafts due to the automatic clutch being released. Thus, the meshing force of the gear pairs is increased, so that it is not possible to perform the shift disengagement. Consequently, a shift stroke becomes stagnant.
In order to solve the above problem, according to Patent Document 1, torque at the input shaft-side of the transmission and torque at the output shaft-side of the transmission are detected and starting time of the shift disengagement is set so that the shift is disengaged at timing at which the torques are balanced.
Patent Document 1: Japanese Patent Application Publication No. 2010-203586A
According to Patent Document 1, however, since the starting time of the shift disengagement is determined based on the timing at which the torque at the input shaft-side and the torque at the output shaft-side are balanced, the balance time of the torques may be late. In this case, the starting time of the shift disengagement is delayed and the time from a shift transmission starting to a shift transmission completion is prolonged. Thereby, even in a driving situation where the acceleration or deceleration is necessary, the shift transmission is not rapidly made, so that the mileage or operability may be deteriorated.
Also, according to the related art control device for the automatic transmission, as shown in FIG. 14, the shift transmission control starts to thus operate a clutch actuator of the automatic clutch (t1) and a shift actuator is operated at a time point at which the automatic clutch is released to some extent (at a time point at which a clutch stroke reaches a predetermined value or at a time point at which a difference between the number of revolutions of the rotary shaft at the input-side and the number of revolutions of the rotary shaft at the output-side reaches a predetermined value) (t2), so that the shift disengagement operation of the gears starts. In this case, since the clutch release operation (t1) and the shift disengagement operation (t2) are performed with being temporally-deviated, the shift transmission time is prolonged. As a result, even in the driving situation where the acceleration or deceleration is necessary, the shift transmission is not rapidly made, so that the mileage or operability may be deteriorated.